Samantha Stosur continued the rehabilitation of her hardcourt game with a 6-1 7-5 first-round defeat of fellow Grand Slam winner Svetlana Kuznetsova at the Cincinnati WTA and ATP Masters on Monday.
Stosur, who won the US Open in 2011, had seen a dip in form that dropped her out of the top 10 in the WTA world rankings.
The 29-year-old, who also finished runner-up in 2010 at the French Open, had fallen in the third rounds of both Roland Garros and Wimbledon.
She began to make up ground with a hardcourt title eight days ago in Carlsbad, California, beating two-time Australian Open winner Victoria Azarenka.
Stosur needed just 66 minutes to dispatch Russia's Kuznetsova, ranked 29th in the world after several injury plagued seasons.
Stosur broke three times while never facing a break point in the contest. The Aussie arrived in Cincinnati after exiting in the third round in Toronto last week to former Wimbledon champion Petra Kvitova.
The joint event features the elite of both tours, with Toronto champion Serena Williams heading a women's field that includes all top-20 players.
World number three Maria Sharapova will be playing for the first time since a Wimbledon second-round defeat and subsequent healing of a hip injury.
The men's field features Novak Djokovic, Wimbledon winner Andy Murray, Montreal champion Rafael Nadal and fifth-ranked Roger Federer, a five time champion in this hardcourt US Open tuneup.
In other women's opening-day play, American Lauren Davis beat Czech Klara Zakopalova 7-6 7-6 while compatriot Vania King eliminated France's Kristina Mladenovic 6-4 6-3. Romanian Simona Halep opened her campaign with a 6-7 6-1 6-1 victory over Taiwan's Hsieh Su-Wei.
Halep booked a second-round match with eighth-seeded Wimbledon champion Marion Bartoli of France.
In men's play, Spanish 13th seed Nicolas Almagro lost in a Masters first round for the second week in succession as he went down to Bulgarian Grigor Dimitrov 7-6 6-4.
German Philipp Kohlschreiber gave former finalist Mardy Fish a rough welcome back to the ATP, handing him a 7-5 6-2 defeat that won't help the 31-year-old American's effort to regain confidence after a 2012 heart scare.
"I feel all right, I just have an awful long way to go tennis-wise," Fish said. "It shows you how amazing Rafa has been coming back after seven months off. To do what he's done (eight titles this season in his comeback) is just not normal.
"Matches like today and days like today really make you question how far you've got to go, if there's still that sort of fire and drive that you need, and that's tested. This is not an easy game in that regard at all. When you get to be out here for that long, for this long, it becomes challenging for sure."
